The present invention relates to hydraulic piston pumps in which the pistons are driven in a reciprocating motion by bearing on a cam, said cam being of any appropriate form, in particular, but not limited thereto, the form of a skew plate.
In this type of pump the pistons may be "axial", that is, parallel to the axis of the pump, or "radial", that is, perpendicular to the axis of the pump and arranged along radii. In a general manner, radial pistons take support on one or more cams, carried by the drive shaft, while axial pistons are supported an on a skew plate, sometimes called oscillating plate.
It is known practice to arrange a suction valve on each piston, and to arrange a discharge valve downstream of each bore in which a piston moves. Thus, when the piston is extracted from its bore, the hydraulic liquid is admitted into said bore through said piston by a non-return valve integrated in the piston, and when the piston is driven into its bore, the liquid is forced out of it.